Connection for precast concrete girders and beams



1951 A. HENDERSON 2,580,174

CONNECTION FOR PRECAST CONCRETE GIRDERS AND BEAMS Filed Dec. 31, 1943INVENTOR. E T HENDERSON BYMIWJ awd ATTORNEY;

to the recess.

Patented Dec. 25, 1951 CONNECTION FOR PRECAST CONCRETE GIRDERS AND BEAMSAlbert Henderson, Pittsburgh, Pa., assignor, by mesne assignments, toPeoples First National Bank & Trust Company, Pittsburgh, Pa., a nationalbanking association Application December 31, 1948, Serial No. 68,575

2 Claims.

This invention relates to a building construction utilizing precastconcrete members as girders and beams, and, in particular, to aconnection between the girders and beams. This application is acontinuation of my copending application Serial No. 629,797, filedNovember 20, 1945, now abandoned.

It is desirable in constructing buildings of precast concrete members tohave the upper surfaces of the floor beams flush with the upper surfacesof the girders on which they are supported. A simple manner ofaccomplishing this result is to form pockets in the girders adapted toaccommodate the ends of the beams. This practice has always beenconsidered objectionable heretofore, however, because the voids orpockets required to receive the beam ends involve a reduction in thesectional area of the girder available to withstand compression andshear stresses. I have invented a novel connection by which beams mayhave their ends disposed in pockets spaced along the girders withoutsubstantial loss in the compression area or the strength of the girderin resistance to shear.

I provide for compensating for the loss of strength in the upper portionof the girder due I provide for placingof the beam end in compressionbetween the opposed faces of the recess in the girder when the beam isloaded. I preferably supportingly connect the beam end With the girderonly at the generally vertically 7 extending faces of the recess.

through the generally verticall extending faces of the recess and theloss of strength in the upper portion of the girder due to the recess iscompensatcd for. The side faces of the beam end disposed within therecess are preferably in supported relationship with the side faces ofthe recess while the bottom of the beam end disposed within the recessis preferably out of supported relationship with the bottom of therecess. I may position the side faces of the beam end disposed withinthe recess in face-to-face relationship vertically extending faces.

with the side faces of the recess and interpose between the side facesof the beam end disposed within the recess and the side faces of therecess means for supportingly connecting the beam end with the sidefaces of the recess. The side faces of the beam end disposed within therecess may be in surface-to-surface contact and supported relationshipwith the side faces of the recess.

The recess may have generally vertically exending faces which convergetoward each other in a generally downward direction, and the beam endmay have similarly disposed faces. The vertically extending faces of therecess and the opposed faces of the end portion of the beam may bothhave substantially horizontally extending corrugations. Loadtransmitting means may be disposed in the gap between the opposed facesof the end portion of the beam and the recess. The load transmittingmeans may comprise preformed load transmitting members or afillingformed in situ and filling the gap between the opposed faces ofthe end portion of the beam and the recess. The filling may be acementitious filling, such, for example, as grout, and in certain casesexpaneling grout may be used.

The recess in the girder is open at the top and at least one side of thegirder and has generally The recess may be of dovetail shape in thehorizontal direction, beingnarrower at its mouth than at a portioninwardly from its mouth, and the beam end lying in the recess may be ofdovetail shape conforming generally to the dovetail shape of the recess.

Means may beprovided interengaging the beam end and girder preventingendwise displacement of the beam from the recess. Compressible nonloadtransmitting filling material may be disposed between the bottom of thebeam and the bottom of the recess or the bottom of the beam may simplybe spaced from the bottom of the recesse In a preferred embodiment of myinvention I provide pockets or notches spaced along both sides of agirder adapted to receive the ends of sary to use expanding grout. Whenexpanding grout is used it expands as it sets and firmly fixes the beamends in the girder pockets under compression, thus making up for theloss of sectional area which would otherwise result from the formationof the pockets in the girder. The corrugations in the pockets and beamends make up for the loss of shear strength which would otherwise resultfrom the presence ot the pockets although in certain structures thecorrugations may be dispensed with.

As above indicated, compressible material may, if desired, be disposedbetween the bottoms of the beams and the bottoms of the pockets so thatthe load on the beams will be transmitted to the girder substantiallyexclusively through the sides of the pockets, the beam ends being incompression therein.

A complete understanding of the invention may be gained from thefollowing detailed description which refers to the accompanying drawingsillustrating certain present preferred embodiments thereof. in thedrawings,

Figure 1 is a partial plan view of a girder and alined beams extendingfrom opposite sides thereof;

Figure 2 is a transverse section through the girder along the plane ofline iIII of Figure 1 with the beam on one side of the girder omitted;

Figure 3 is an end elevation of one of the beams;

Figure 4 is a partial side elevation of a girder showing a modified formof pocket;

Figure 5 is an end elevation of a beam adapted to have its end disposedin the pocket of the girder shown in Figure 4;

Figure 6 is a partial transverse section through a'further modified formof girder;

Figure 7 is a partial side elevation of a beam having its end adapted tobe disposed in the pocket at the side of the girder of Figure 6;

Figures 8 and 9 are views corresponding respectively to Figures 4 and 5showing a girder and beam of further modified construction; and

Figure 1c is a perspective view of the end or" the beam shown in Figure5.

Referring in detail to the drawings, a precast reinforced concretegirder it has recesses or pockets I! in the sides thereof spaced alongits length. The girder has lower reinforcing bars l2 and upperreinforcing bars i3 with stirrups I4 extending around the bars and.spaced longitudinally of the girder. As shown in Figure 1, the pockets Hmay be of dovetail form in plan although this is not necessary and thegenerally vertical transverse walls of the pockets may be at rightangles to a vertical plane extending longitudinally of the girder. Thepockets H are shown as having horizontal corrugations E5 in their sidesand inner ends.

The pockets 1 i are adapted to receive the ends of precast reinforcedconcrete beams [8. The ends of the beams as shown are also of dovetailform in plan, this form of beam end being employed when the pockets areof dovetail 'form. The ends of the beams and the sides thereof adjacentthe ends have corrugations H which when the beams are in position withtheir ends in the girder pockets extend generally horizontally orparallel to the corrugations [5.

When the ends of the beams have been disposed in the pockets H thespaces between the beam ends and the pocket walls, indicated at l8, "arefilled with expanding grout. This material expands as it sets, therebydeveloping compression between the sides of the pockets and the sides ofthe beams adjacent the ends thereof as well as between the ends of thebeams and the inner walls of the pockets. In order to prevent the beamends from being pushed out of the pockets I may provide transverse slotsis in the upper faces of the beams adjacent the ends thereof andlongitudinal slots 2c in the upper face of. the girder on opposite sidesof each pocket H. A key or tie rod 25 disposed in the slots Is and 2t)as shown in Figures 1 and 2 prevents endwise displacement of the beams.When the grout has set the dovetail shape of the beam ends and thepockets prevents displacement of the beams outwardly of the pockets.

The ends of the beams are preferably stepped as shown at 22 so that thebottoms of the beams do not bear directly upon the bottoms of thepockets ii. If desired, a compressible filler 23 may be disposed belowthe beam ends, although the space between the bottoms of the beam endsand the bottoms of the pockets may simply be left void. In either casethe load applied to the beams is transmitted to the girder exclusivelythrough the generally vertically extending faces of the girder recessesor pockets and, in a corrugated structure such as that shown in Figure2, through the corrugations in the adjacent surfaces of the beam endsand the girder pockets and the grout therebetween. The effect of thisarrangement is that when the beams are loaded their ends and thesurrounding grout compensate for the loss of section of the originalgirder caused by the formation of the pockets therein. It will beapparent that the grout filling, either by virtue of the pressureresulting from its expansion or the compression introduced therein bythe load on the beams, will transmit the compression stress on the upperportion of the girder section from one side of each pocket through thebeam end positioned therein to the other side of the pocket. Similarly,by virtue of the corrugations formed in the walls of the pockets and onthe ends and sides of the beams, the beam ends compensate almostentirely for the loss of strength of the girder in resistance to shearwhich would otherwise result from the presence of the pockets.

Figure i shows a girder 25 having pockets 2% in its sides, spacedlengthwise thereof. pockets 26 have corrugations 21 formed in the sidesand inner ends thereof. The sides of the pockets converge downwardly.

Figure 5 shows a beam 28 having downwardly tapering end portions 29provided with horizontal corrugations 35. The end portions of the beamare adapted to fit in pockets such as the pockets 2%; of the girder 25.The resulting construction is thus generally similar to that shown inFigures 1 and 2 except that the sides of the girder pockets and the beamends slope inwardly toward the bottom instead of being vertical. Thisconstruction provides increased compression on the grout filling thespace between the walls of the girder pockets and the side and end facesof the beams when the latter are loaded.

As a further modification of the construction of Figures 4 and 5, thecorrugations 2i and 36 may be omitted, i. e., the sides and inner endsof the pockets 26 and the ends of the beams 28 and the sides thereofadjacent the ends may be plane surfaces. Such a structure is shown inFigures 8 and 9 in which parts corresponding to parts in Figures 4 and 5are designated with the same reference numerals but each with a The,

prime aifixed. In each case the bottom of the beam is preferably spacedabove the bottom of the pocket as in Figure 2. In the structures ofFigures 4, 5, 8 and 9 the downwardly converging sides of the beam endsexert lateral pressure on the sides of the pockets through the groutfilling when the beams are loaded, thus transmitting nearly the fullcompression in the upper portion of the girder across the pockets. Thetight fit between the girder and beam, furthermore, largely compensatesfor the shear strength lost by forming the pockets in the girder. Groutor other load transmitting means may be disposed between the beam ends29 and the pockets 26' in use of the structures of Figures 8 and 9 ornot, as desired. The result sought is accomplished by the tight wedgingof the beam ends int-o the pockets since the beam ends andpockets aremade to conform to each other in shape and compression in the upperportion of the girder is transmitted continuously across the beam ends.When grout or other load transmitting means is to be disposed betweenthe beam ends 29 and the pockets 26 in use of the structures of Figures8 and 9 the beam ends will have the proportions indicated by the solidlines 29' in Figure 9 while when no grout or other load transmittingmeans is to be disposed between the beam ends 29 and the pockets 26 inuse of the structures of Figures 8 and 9 the beam ends will have theproportions indicated by the chain lines 29' in Figure 9.

Figure 6 shows a girder 3! having pockets 32 therein with corrugations33 in the walls thereof. The corrugations, as shown, are sloped insteadof horizontal. Figure 7 shows a beam 3 generally similar to the beam itexcept that the corrugations 35 on the ends and the sides adjacent theends thereof are sloping instead of horizontal. The slope of thecorrugations 33 and 35 provides increased resistance to pulling out ofthe beams from the girder pockets in which their ends are disposed. Thecorrugations on the beam ends may slope in the same direction as thoseon the girder pockets or in the opposite direction.

It will be understood that the modified forms of girder and beamconstruction shown in Figures 4 through 9 have the same advantages asthe construction of Figures 1 and 2. Since the compression area of thegirder section and the strength of the girder in shear are restored bythe construction disclosed almost to the full original values, i. e.,those of a girder without pockets, it is possible for the pockets toextend clear across the full width of the girder. This is desirable insome cases. It will be understood that, in such a modification, the endsof alined beams extend inwardly substantially to the centrallongitudinal vertical plane through the girder.

Although I have illustrated and described certain embodiments of myinvention, it will be recognized that changes in the details disclosedare to be comprehended within the scope of the following claims.

I claim:

1. A building structure comprising an elongated reinforced concretestructural member oriented generally horizontally with a portion thereofadjacent its upper edge in compression, the structural member having arecess formed in said portion thereof, the recess having opposedgenerally vertically extending faces each of which has at least aportion extending generally downwardly and inwardly, the recessweakening the structural member, and a second elongated precastreinforced concrete structural member oriented generally horizontallyhaving a part thereof disposed within the recess of the first mentionedstructural member, said part of the second structural member havingopposed generally vertically extending faces each of which has at leasta portion extending generally downwardly and inwardly opposed to asimilarly extending portion of one of the faces of the recess of thefirst mentioned structural member, the structure having connectionsunder compression between said respective opposed face portions of therecess of the first mentioned structural member and of said part of thesecond structural member through which said part of the secondstructural member is supported entirely, said connections and said partof the second structural member transmitting compression across therecess longitudinally of the first mentioned structural member to atleast largely compensate for the weakening of the first mentionedstructural member by formation of the recess therein.

2. A building structure comprising an elongated reinforced concretestructural member oriented generally horizontally with a portion thereofadjacent its upper edge in compression, the structural member having arecess formed in said portion thereof, the recess having opposedgenerally vertically extending faces each of which has therein generallyhorizontal corrugations, the recess weakening the structural member, asecond elongated precast reinforced concrete structural member orientedgenerally horizontally having a part thereof disposed within the recessof the first mentioned structural member, said part of the secondstructural member having opposed generally vertically extending faceseach of which has therein generally horizontal corrugations, the facesof the recess of the first mentioned structural member beingrespectively opposed to the faces of said part of the second structuralmember, and cementitious material in loadtransmitting relationshipbetween the faces of the recess of the first mentioned structural memberand the respective opposed faces of said part of the second structuralmember through which said part of the second structural member issupported entirely, said cementitious material and said part of thesecond structural member transmitting compression across the recesslongitudinally of the first mentioned structural member to at leastlargely compensate for the weakening of the first mentioned structuralmember by formation of the recess therein.

ALBERT HENDERSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 409,893 Wray Aug. 27, 1889918,699 Ransome Apr. 20, 1909 1,423,949 Laughlin July 25, 1922 1,673,628Krummel June 12, 1928 1,739,102 Strauss Dec. 10, 1929 2,414,738Henderson Jan. 21, 1947 FOREIGN PATENTS Number Country Date 35,216Denmark of 1925

